Cutter tool

Abstract

A cutter tool that includes a shank by which the tool is releasably retainable within a tool holder, an enlarged shoulder or heel provided at one end of the shank and adapted, in use, to abut a seating surface of a tool holder and limit the penetration of the tool holder into a receiving aperture of the tool holder, and an integral blade provided beyond the enlarged shoulder or heel and terminating in a carbide or other tip. The tool is provided with a zone of weakness such that if subjected to fracture forces, a fracture will be encouraged to propagate from the zone of weakness in a particular desired manner.

What we claim is: 
     
       1. A cutter tool for attachment to an excavating machine for working a material to be excavated, the cutter tool comprising a shank releasably retainable within an aperture in a tool holder mounted on the excavating machine, a head for contacting the material to be engaged during use, the head being fixed at one end of the shank to define an interface between the shank and the head, the head having a shoulder to limit the penetration of the cutter tool into the aperture of the tool holder, and a zone of weakness at the interface between the shank and the head such that when the cutter tool is subjected to fracture forces a fracture will be encouraged to propagate through that interface and the head broken from the shank. 
     
     
       2. A tool as claimed in  claim 1 , wherein the zone of weakness is defined by a slot formed in the tool at the interface between the shank and the head. 
     
     
       3. A tool as claimed in  claim 2 , wherein the shank has a longitudinal axis, and the slot extends in a direction perpendicular to the longitudinal axis. 
     
     
       4. A cutter tool for attachment to an excavating machine for working a material to be excavated, the cutter tool comprising a shank releasably retainable within an aperture in a tool holder mounted on the excavating machine, a head for contacting the material to be engaged during use, the head being fixed at one end of the shank, the head having a shoulder to limit the penetration of the cutter tool into the aperture of the tool holder, and a zone of weakness such that when the cutter tool is subjected to fracture forces a fracture will be encouraged to propagate through the zone of weakness and the shoulder be broken from a portion of the shank. 
     
     
       5. A tool as claimed in  claim 4 , wherein the zone of weakness in the tool is at an interface between the shank and the head. 
     
     
       6. A tool as claimed in  claim 4 , wherein the zone of weakness is defined by a slot formed in the tool at an interface between the shank and the head. 
     
     
       7. A tool as claimed in  claim 4 , wherein the shank has a longitudinal axis, and the slot extends in a direction perpendicular to the longitudinal axis. 
     
     
       8. A tool as claimed in  claim 4  which has a front surface, a rear surface and side surfaces, wherein the front surface faces in a direction of travel when in operation, and the zone of weakness is defined by a slot that opens only in the front surface and in the side surfaces to the depth of the slot.